we're all familiar with the price of things by weight (either Kg or lbs depending where you're from) but most of us don't think of our photographic gear this way. Some time ago I did look at that with respect to my Panasonic G1 and a Canon EOS 5DMk ii and found that the image quality was not so different but the price per Kg was ... I thought I'd expand on that post with some more data and in a chart.
its sort of interesting that there is a reasonably linear price / kg change along the line from G1 (price when new) to Sony A7ii (price when new too) and some standouts in the "dear" range as well as the lower end.
What's also interesting is that I seem to also buy on the more cost effective side of things (interesting coincidence really).
I should probably toss in megapixels into that but to me they are about equal as image making tools.